Unify reserved word checking and update error messages

[danez]

Q	A
Fixed Issues?
Patch: Bug Fix?	(y)
Major: Breaking Change?	n
Minor: New Feature?	n
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

When checking for reserved words we currently do multiple checks: isReservedWords, isReservedWordsStrict and isReservedWordsStrictBind
This all is actually one check, but the list of reserved words changes depending on the context defined by inModule, strict and isBinding

So what this PR simply does is make it unnecessary to check all the different types of reserved words and instead only check against ONE list of reserved words for non-strict, strict or strict-binding. All this list contain their previous list:

non-strict: [..]
strict: non-strict + [...]
strict-binding: strict + [...]

For performance this is good because we do only one lookup against one list instead of multiple lookups. The non-strict "list" is not really a list because it contains the logic for inModule. I could have multiplied this out and created more lists (non-strict, non-strict-in-module, strict, strict-in-module, strict-bind, strict-bin-in-module) but decided not to.

[existentialism]

LGTM after fixing enum test failure

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/9956/

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/9899/